Research start date: October 22, 2024

Research status: Open

Recall issued: No

This is a fast-moving outbreak investigation. Most sick people report eating McDonald’s Quarter Pounder burgers and investigators are working quickly to confirm which food ingredient is contaminated. McDonald’s has rounded up ingredients for these burgers and they won’t be available for purchase in some states.

United States

  • Fallen: 49
  • Hospital admissions: 10
  • Deaths: 1
  • States: 10

This is a fast-moving outbreak investigation. Most sick people report eating McDonald’s Quarter Pounder burgers and investigators are working quickly to confirm which food ingredient is contaminated. McDonald’s has rounded up ingredients for these burgers and they won’t be available for purchase in some states.

Summary of the situation

CDC, FDA, USDA FSIS and public health officials in multiple states are investigating an outbreak of E.coli O157:H7 infections. Most people in this outbreak report eating the Quarter Pounder hamburger at McDonald’s before becoming ill. It is not yet known which specific food ingredient is contaminated.

McDonald’s is working with research partners to determine which food ingredient in Quarter Pounders makes people sick. McDonald’s has stopped using fresh-cut onions and quarter-pound beef patties in several states while an investigation continues to identify the ingredient causing the disease.

Contaminated food

Quarter pounder burgers from McDonald’s are making people sick, with most illnesses occurring in Colorado and Nebraska.

  • Quarter Pounder burgers will be temporarily unavailable in some states.
  • Researchers are trying to confirm which ingredient in these burgers is making people sick and whether it has spread to other restaurants or stores.
  • McDonald’s reported to the CDC that it has stopped using fresh sliced ​​onions and quarter-pound beef patties in several states. McDonald’s is proactively implementing these changes as investigators work to confirm the contaminated ingredient. Quarter pound beef patties are only used on Quarter Pounders. Fresh chopped onions are primarily used on Quarter Pounder burgers and not on other menu items.

What to do

McDonald’s has stopped using fresh-cut onions and quarter-pound beef patties in several states to protect their customers while a source of illness has been confirmed.

Call your healthcare provider if you have eaten a McDonald’s Quarter Pounder hamburger and are experiencing serious symptoms E.coli symptoms:

  • Diarrhea and fever higher than 102°F
    • Diarrhea lasting more than 3 days that does not improve
    • Bloody diarrhea
  • So much vomiting that you can’t keep the fluids down
  • Signs of dehydration, such as:
    • Not much urination
    • Dry mouth and throat
    • Dizzy feeling when getting up

Symptoms of E.coli

  • Most people are infected with the production of Shiga toxin E.coli suffer from severe stomach cramps, diarrhea (often bloody) and vomiting.
    • Symptoms usually begin 3 to 4 days after ingesting the bacteria.
    • Most people recover without treatment after 5 to 7 days.
  • Some people may develop serious kidney problems (hemolytic uremic syndrome, also called HUS) and require hospitalization.
  • For more information about E.colisee the E.coli Questions and answers page.



Content source:

National Center for Emerging and Zoonotic Infectious Diseases (NCEZID)